Figure F54. Total alkalis (Na₂O + K₂O) vs. SiO₂ abundance. A. Site 1137 basalts compared to those from other parts of the Kerguelen Plateau. The boundary between tholeiitic and alkalic basalts from Macdonald and Katsura (1964). The more altered Site 1137 basalts plot distinctly above the general field for Site 1137 because of higher alkali content. Data sources are Davies et al. (1989), Weis et al. (1989), Alibert (1991), Mehl et al. (1991), Salters et al. (1992), Storey et al. (1992), Mahoney et al. (1995), and this study. B. Site 1137 basalts and more evolved rocks; chemical classification and nomenclature of Le Bas et al. (1986).